FIG. 1 (Prior Art) is a simplified diagram of circuitry found in some personal computers. Personal computer 1 receives a 110 volt AC (Alternating Current) RMS (Root Mean Square) supply voltage VS 2 via terminals 3 and 4. A Switching Mode Power Supply (SMPS) 5 converts the AC supply voltage VS 2 into a rough DC voltage VI 6. The DC voltage VI 6 is present between supply voltage conductor 7 and ground conductor 8. In one example, the DC voltage VI is +12 volts DC. The personal computer further includes multiple buck converters 9, 10 and 11 that may be physically organized around a CPU (Central Processing Unit) 25 on the motherboard of the personal computer. Each buck converter converts the rough DC voltage VI into a lower DC voltage VO 12. In one example, the lower DC voltage VO 12 is 1.0 volt DC and is supplied onto the VCC supply voltage terminals 13, 14 and 15 of the CPU 25. The buck converters may be of conventional design. In one example, each buck converter includes an input capacitor, a main switch, a second switch (sometimes referred to as a free-wheeling switch), an inductor, an output capacitor, and a control circuit. Buck converter 9, for example, includes an input capacitor 16, a main switch 17, a free-wheeling switch 18, an inductor 19, an output capacitor 20, and a control circuit 27.
FIG. 2 (Prior Art) is a waveform diagram that illustrates operation of the three buck converters 9, 10 and 11 of FIG. 1. The three control circuits of the buck converters cause the main switches of the buck converters to be turned on and off in the phased relationship illustrated in FIG. 2. As a result, the inductor currents 21, 22 and 23 also have a phased relationship. The output capacitors of the buck converters are coupled together in parallel. Conductor 24 couples the output voltage nodes of the three buck converters together at a location near the CPU. Accordingly, the three buck converters together share the function of supplying the necessary supply current ICC to the CPU 25 at the desired VO output voltage required by the CPU. Due to the phased relationship of the switching of the buck converters, the overall supply current ICC as supplied to the CPU has a smaller ripple current 26 than if just one buck converter of similar size were used. In some cases, the three control circuits are parts of the same single control integrated circuit.